1. Field of the Invention
The present invention relates to a waveguide phased array antenna apparatus and in particular to a waveguide phased array antenna apparatus for changing the phase of an electromagnetic wave propagating through each waveguide thereof.
2. Description of the Prior Art
In recent years, to ensure a radio communication line between a fixed station on the ground and a mobile station such as an automobile or airplane, a mobile satellite communications system with an artificial satellite employed as a transponder has been put into practical use. In this field, a waveguide phased array antenna has been used to automatically track the artificial satellite.
A waveguide phased array antenna is an electronic scanning antenna that scans a radiant beam by electronically changing the phase of the electromagnetic wave supplied to the individual radiating waveguides that make up a radiating waveguide array. A radiant beam means an electromagnetic wave radiated from an antenna in a predetermined direction.
FIG. 1A is a plan view of a conventional waveguide phased array antenna unit. The conventional waveguide phased array antenna unit is composed of a radiating waveguide array 10 with a plurality of radiating waveguides 11 arranged in parallel and each radiating waveguide having a plurality of radiating elements 12. Each of the radiating waveguides 11 is coupled to a phase shifter 13 which is in turn coupled to a power distributor waveguide 14 for distributing the power from a feeding section 15 to each radiating waveguide 11.
The respective phase shifters 13 control the phase of the propagating radio wave. The power is supplied from the feeding section 15 and is distributed to the radiating waveguides 11 through the phase shifters 13. The respective phase shifters 13 control the phases of the propagating radio waves supplied to the radiating waveguides 11 so that the radiating waveguides 11 radiate radiant beams in phase with each other to allow for radiation in phase corresponding to the phase at the feeding point.
Meanwhile, a waveguide ferrite phase shifter is widely used as the phase shifter 13. As a typical example, there is shown a waveguide latching phase shifter in FIGS. 1B and 1C.
The waveguide latching phase shifter is made by using a ferrite toroid 17 having dielectric 18 therein with two ferrite plates integrated to form a closed magnetic path. It is a phase shifter in which use is made of the difference in ferrite magnetic permeability in two magnetized states whose polarity switches in response to a pulsating current flowing through a lead wire 16.
However, the above waveguide latching phase shifter is large in volume. Because it employs a waveguide latching phase shifter as the phase shifter 13, a conventional waveguide phased array antenna unit has a problem in that the unit ultimately becomes large in size.